A common way to optimize the usability and the support for the user is to increase the knowledge of the device and application about the user and the environment. Storing user profiles and application history is one approach to enhance usability for the software. Knowledge about the environment in that the device will be most likely deployed is used when designing the hardware of devices. A variety of devices is offered, each of these devices designed to meet different and specific requirements given in a certain environment (e.g. lightweight, water resistant, shock proved, large display, minimized power consumption, etc.).
In addition our approach is to use sensors to acquire information about the environment and hence the situational context in which a device is operated. To implement this type of context-awareness in mobile applications we have equipped ultra-mobile devices with environment-sensing capabilities. This is quite in contrast to smart environments, such as active badges ( Beadle et al. 1997, Harter and Hopper 1998), as it rather smartens up devices than their environments, providing context-awareness in any environment. Location as context is introduced by Schilit et al. ( 1994) and further discussed by Leonhard et al ( 1996).
Basic and cheap sensors are used to sense environmental conditions, such as noise-level, light conditions, or device orientation. Having this context knowledge the device can adapt to these conditions and hence enhance the usability. Using output and input filters according to the noise-level and type, controlling the brightness of a display based on the light conditions, and considering the device orientation when displaying content on a small display are typical examples for such applications.
In the next section we will introduce a more general concept of context, while the remainder of this section presents an example implementation for an orientation aware UI.
The device orientation can be determined with a simple and cheap sensor, nevertheless this knowledge can provide a more efficient human computer interface.
Displays often have a rectangular shape with different length and width. Therefore it is possible to display documents and objects in landscape or portrait. For a stationary computer (e.g. a workstation with a 21" screen) this is less important - a document can be displayed in both ways with good quality on the screen. But considering handheld devices with very limited screen real estate the orientation can be of significance for the usability.